Spark plug



R. T. HURLEY April 2, 1935.

SPARK PLUG Filed March 13, 1930 IN VENT 0R fioy Z Hur/ey w W-% ATTORNEYSPatented Apr. 2, 1935 1,996,421

UNITED STATES PATENT OFFICE- sraax rnuc Roy '1. Hurley, Dobbs Ferry, N.Y., alalgnor to Hurley-Townsend Corporation, New York, N. Y., acorporation of Delaware Application March 13, 1930, Serial No. 435,461

' 10 Claims. (Cl. 123-169) This invention relates to spark plugs and hasA sheet of compressible, heat-resisting, insufor an important object theprovision of a spark lating material, such as mica, is next snugly plugwhich will be well sealed at all times against wrapped around the sleeve6 in the form of a the escape of gases through it and which will, asmultiple-pLv tube 9. Upon this tube 9 the lower a consequence, be welladapted to avoid overend iii of the insulator is built up of washers 5heating evenunder the exacting conditions imof suitable insulatingmaterial, such as mica. posed in heavy duty engines, such as those em-The nut 4 is then impaled upon the tube and the ployed in airplanes andin racing automobiles. pp r nd II 0! h insulator is built p y p Otherobjects and advantages will hereinafter ing upon the tube furtherwashers of mica or I0 appear. other suitable material. As thusassembled, the

In the drawing forming part f thi in nut 4 does not bind upon the tube 9but fits it tion, rather snugly.

Figure 1 is a vertical sectional view taken cen- The Cali-r81 electrode18 next inserted in e trally through a spark plug embodying feat sleeve8 from the lower end thereof. The cen- I5 of the invention. tralelectrode comprises a shank l2 and a nose Figure 2 is a vertical,sectional, damn i It, the nose being larger than the shank, but throughan expandible sleeve employed in t of such small mass that the heatabsorbed by it spark plug of Figure 1; may be rapidly and eflicientlyconducted away, Figure 3 is a plan view of the sleeve of Figprincipallyby the shank I! and the sleeve 6. ure 2; The central electrode isdesirably made of steel 20 Figure 4' is a sectional view t k n on t lineor other suitable material that will resist oxidal-l of Figure 2,looking in the direction of the tion by the combustion in the engine.The nose arrows; and I3 carries a sparking tip it of suitable material,

Figure 5 is a vertical, sectional view through a such s ic an a ese wimodified form of expandlble sleeve hi may be Prior to the insertion ofthe central electrode, 25 employed. the sleeve, insulator and nutassembly is longi- The illustrative spark plug comprises an tudinallycompressed, and this pressure is-maintemally threaded shell I adapted tobe thread d tained throughout the insertion of the electrode. into amotor. The shell I carries a spark eiee- The shank I2 of the centralelectrode is of a trode 2 which forms one terminal of the spark diameterto 8 mi Within the ungmoved 30 Ban. An insulator and central electrodeassemlower end of the sleeve It may he s r in bly 3 comprises anexternally threaded u; 4 the sleeve readily therefore, but when itreaches which is screwed t ghtly into the shell I to cothe internal ribsformed by grooving of the act with the shell in firmly clamping an intr. exterior of the sleeve, it must be driven. This posed gasket 5 toform a tight seal. The nut driving of the electrode through the sleeveelimi- 35 4 serves as a retaining and supporting memb nates the groovesand expands the grooved porfor the central assembly 3. tion of thesleeve to the diameter of the un- The central assembly 3 also comprisesan exmo p t on. Such expans on of the s e panded sleeve 6, (see Figures2 and 3) of malsimultaneously applies circumferential tension 40 leablemetal having high heat conductivity, such fi "41131 W to the tube W811 930 that 40 as copper. This sleeve is provided with a flange the tubewall is pressed with considerable force I' at the lower end thereof. Itis upon this sleeve between thelsleeve and the nut The Shank that thecentral assembly is built up. The leeve and the sleeve 8 have at leastas high coeflit may be initially a cylindrical tube provided cients ofheat expansion as the nut 4, so that with the flange I, but before thesteps of incor-' this pressure is not relieved when the spark plug 45porating it in a spark plug are begun, longibecomes heated in use.tudinally extending grooves I are formed in the After the insertion ofthe central electrode, outer face of the tube. The grooves l terminatethe conductive terminal II is placed upon the a short distance above thelower end of the upper end of the shank 42 and the upper end 60 sleeve.Since the formation of the grooves (115- of the shank is upset, as shownat it, to hold places some of the metal inward, the outside the parts inassembled relation and under presdiameter 0! that length of the sleevein which sure the grooves have been formed is reduced by the Thedescribed construction is efficient under formation'of the grooves andis less than that all operating conditions and is especially eflicientof the \mEI ved lower end Po tion. under heavy duty conditions ofoperation because and a radially e member portant that the shank beprotected against the circulation of hot gasm around it, since theabsorption of heat by the shank from any source other than the electrodenose will necessarily reduce the temperature gradient of the shank. Itis of especial importance that the circulation of gases between theshank and the nut be avoided because the mass of metal forming the nutserves as an efiective means of withdrawing heat from the shank at thepoint where the insulation is of minimum thickness. The describedconstruction is efiective to maintain the shank and sleeve in asintimate heat-transferring relationship with the nut i as is consistentwith maintaining good electrical insulation between the shank'and thenut.

In Figure 5 a modified sleeve 6A is illustrated. This sleeve is notgrooved like the sleeve 8 but includes a portion 5 I of reduceddiameter. The sleeve is assembled with the insulator and nut eieinentsin the same manner as the sleeve 6 already described. It would not bepracticable to drive the electrode rod directly into this sleeve for thepurpose of expanding it. Such expansion may be accomplished, however, byintroducing a steel ball N in advance of the electrode I2 and driving itthrough the reduced portion of the sleeve in advance oi the electrode02. The construction and operation of the finished assembly is the sameas that illustrated in Figure 1.

While I have illustrated and described in detail certain preferred formsoi my invention, it is to be understood that ches may be made thereinand the invention embodied in other structures. I do, not. therefore,desire to limit myself to the specific constructions illustrated, butintend to cover my invention broadly in whatever form its principle maybe utilized.

1 claim:

1. In a spark plug the combination with a shell, of a nut threaded inthe shell, a central electrode, a tube oi insulating material interposedbetween the central electrode and the nut, snugly fitting the electrodeand =1 sulating tube against the nut.

2. In a spark plug, a central electrode, a tub of insulating materialsm'rounding the same, a metallic retaining member surrounding the tubeof insulating material, and an expansible sleeve interposed between thecentral electrode and the insulating tube and expanding the said sleeveinto firmly sealed engagement with the metallic retaining member.

3. In a spark plug, the combination with a central electrode 0! a tubeof insulating material surroimding the a metallic retaining mem-' bersurrounding the tube of ting material,

and means including an expansible metal sleeve member cooperating withthe electrode simultaneously to stretch the insulating tubecircumferentially and to compress it radially against the metallicretaining member to form an eflective seal.

4. In a spark plug, the combination with a central electrode and ametallic retaining member surrounding the same, of an insulating tubeinterposed between the electrode and therevtaining member and anexpansible sleeve member positioned within said tube and maintainedunder circumferential tension and under radial compression for forming aseal.

5. In a spark plug, the combination with a central electrode, 01' aretaining member surrounding the electrode, and a sealing tubeinterposed between the electrode and the retaining member and anexpanding sleeve interposed between the sealing sleeve and the electrodeand maintaining the tube under circumferential tension and under radialcompression for forming a seal.

6. In a spark plug, in combination, a central electrode having acylindrical shank, an expand-. ing sleeve surrounding the shank, aninsulating tube on the sleeve, and a heat conductive retaining membersurrounding the tube, the tube being expanded by the sleeve and pressedby it into sealing engagement with the retaining member.

7. In a spark plug, in combination, a central electrode having acylindrical shank and a nose larger than the shank, an expanding sleevesurrounding the shank, an insulating tube on the sleeve, and a heatconductive retaining member surrounding the tube, having no greatercoeflicient of expansion than the electrode, the tube being expanded bythe sleeve and pressed by it into sealing engagement with the retainingmember.

8. An expanding sleeve for use in spark plugs having a circumferentialflange portion at one of its ends and a tubular portion, the end of thetubular portion adjacent the 'flange being ungrooyed and the remainderoi the lengthoi' the tubular portion being externally, longitudinallygrooved.

9. An expanding sleeve for use in spark plugs having a circumferentialflange portion at one of its ends and a tubular portion, the end of thetubular portion adjacent the flange being cylindrical and of a diameterto receive the spark plug electrode snugly, and the remainder oi thelength 01' the tubular portion being of less diameter, so that it willbe expanded by the driving of the electrode into'it.

10. In a spark-plug, the. combination of a body piece having a centralopening, a metallic quill through said opening, an insulating sleevesurroimding the quill, and a central lmetallic spindle driven into thequill so as to expmd the same to grip the insulating sleeve against thesurrounding surface of the opening in the body piece. ROY 'i'. HURLEY.

